I came across this page which lists PCN contacts for across the UK:
http://www.nsl.co.uk/contact Quote:Northern Ireland Roads Service
0287 0341 235
Parking Enforcement Unit
PO Box 134
Coleraine
BT52 9AF
This is a Coleraine PO Box. The number given, (028) 7034 1235, goes through to the same recorded message as is on the 0845 number.
Please let us know how you get on.